Stop ignoring 400 errors returned by ODL

This commit stops ignoring 400 (Bad Request) HTTP codes returned by ODL
in create and update operations. It also modifies sendjson() because it
doesn't ignore any HTTP error code now.

Change-Id: Id0db2c0c1d8fddfbd16b3ce9476a2358e2ef1e49
Closes-Bug: #1369239
(cherry picked from commit f1507d080d9840e4cb6c1d5cfe5a4b6c1443bd8f)
Merge "Stop ignoring 400 errors returned by ODL" into stable/juno